The present invention relates to paperboard containers for liquid products and more particularly to a method for bonding pour spouts to such containers.
A preferred embodiment comprises a container prepared from a flat blank of paperboard, the outside surface of which is coated with a polymer material and printed with graphics suitable for the packaged product. The polymer material most often used for this purpose is a low surface energy polyolefin such as polyethylene, preferably low density polyethylene (LDPE), although other low surface energy polymers such as polypropylene, could be used. Typical of such containers are gable top or flat top parallelopiped constructions which include a pour opening at the top thereof over which a pour spout fitment may be attached. The pour spout fitment is generally made from a molded plastic material such as polypropylene and includes a flanged base portion which is adhered to the outer surface of the container in alignment with the pour opening. A screw cap is generally provided for the pour spout and additional seals may be provided either over the pour opening itself or over the end of the pour spout beneath the screw cap.
As stated above, in the preferred embodiment of the present invention, the pour spout fitment is located on the outer surface of the container over the pour opening in such a manner that the flange portion of the pour spout fitment may be adhered to the container surface in the region immediately adjacent to the pour opening. In the usual course of manufacture, coated paperboard blanks are printed, side seamed and shipped to the customer where the spouts are affixed to the containers as part of the form, fill and seal operation. Unfortunately, problems have occurred in getting good adhesion between the flange of the pour spout fitment and the paperboard container. These problems result in leaking containers and other unsatisfactory performance.
At least one prior art method has been attempted to achieve a good seal between the pour spout and the container. In U.S. Pat. No. 4,830,273, a reinforcing patch is applied to the exterior surface of the container blank over the pour opening prior to bonding the pour spout flange to the container. Meanwhile in U.S. Pat. No. 4,483,464, projecting rings are provided on the flange which are embedded in the container surface for improved adhesion. Nevertheless, the proper functioning of the container/pour spout combination can still be disrupted either when the container is opened or during use. Thus it is a general object of the present invention to prevent the problems that have occurred in the past and to provide an improved means for bonding pour spouts to containers.